The phenomena of light fluorescence and luminescence, stimulated in surfaces of various types by the impingement of incident light or other radiation, are generally characterized by such fluorescent or luminescent light radiation or emission occuring over or from a relatively large volume, and in an omnidirectional fashion. Such omnidirectional emission from a large volume results in low radiance, making it difficult to capture enough of the emitted energy in optical detector instruments to perform desired analyses, including high sensitivity measurements of the amount of emitted light and of its spectral content.
Though attempts have been made to solve this problem through the use of conventional optical techniques, including optical systems with specular surfaces (mirrors) and appropriate focusing lenses and the like and dedicated luminometers, such have not been totally successful and have had serious limitations in sensitivity.
Underlying the present invention, on the other hand, is a discovery of a rather radical departure from such optical measurement techniques residing in enclosing the fluorescing or luminescing volume within a closely fitting cavity formed of highly reflecting diffuse material walls, remarkably to improve the measurement sensitivity of the detector optical system, viewing as much of the cavity radiant wall as possible.